Developing germ cells in the testis and maturing spermatozoa in the epididymis are largely sheltered from the systemic immune system. Although it is clear that antibodies against sperm surface components can prevent fertilization in vitro, and in the female, it is not clear that circulating anti-sperm IgG in the male will have access to testicular or epididymal spermatozoa. In this proposal we investigate two different approaches to this problem of accessibility. Our first specific aim is to identify Sertoli and epididymal epithelial cell specific plasma membrane molecules using monoclonal antibodies. As these cells are intimately involved in spermatogenesis and sperm maturation and are exposed to the systemic circulation, the identification of cell specific and accessible determinants on their surface could lead, both to significant advantages in our knowledge of these cells and to a means of selective impairment of cell function. We have recently developed a cell culture system in which we can closely approximate the in vivo environment of epididymal or Sertoli cells. Using these dual compartment culture chambers we can realistically assess the effects of specific antibodies or antibody conjugates on cell function. Subsequently cell specific antigens will be purified and polyclonal antibodies generated against them. These will be used to screen cDNA libraries and isolate antigen genes which will then be cloned and sequenced. The last part of the proposal addresses the problem of accessibility in another way. It is well known that dimeric IgA, can be specifically transcytosed across a variety of secretory epithelia. Although this molecule is present in high concentrations in semen it is not known which part of the male reproductive tract are involved in its transport. The demonstration that dimeric IgA can be specifically transcytosed and concentrated by reproductive tract epithelial could have great significance regarding the delivery of anti-sperm antibodies. We propose to measure levels of secretory IgA in various reproductive tract fluids, localize the dimeric IgA receptor by both immunocytochemistry and in situ hybridization and investigate the transcytosis of this molecule by relevant reproductive tract epithelia in vitro.